全文获取类型
收费全文 | 18013篇 |
免费 | 1186篇 |
国内免费 | 1699篇 |
专业分类
林业 | 2611篇 |
农学 | 2568篇 |
基础科学 | 1229篇 |
3180篇 | |
综合类 | 5043篇 |
农作物 | 1203篇 |
水产渔业 | 805篇 |
畜牧兽医 | 2300篇 |
园艺 | 602篇 |
植物保护 | 1357篇 |
出版年
2024年 | 163篇 |
2023年 | 259篇 |
2022年 | 436篇 |
2021年 | 657篇 |
2020年 | 645篇 |
2019年 | 642篇 |
2018年 | 441篇 |
2017年 | 507篇 |
2016年 | 582篇 |
2015年 | 731篇 |
2014年 | 677篇 |
2013年 | 872篇 |
2012年 | 1038篇 |
2011年 | 1170篇 |
2010年 | 1061篇 |
2009年 | 1009篇 |
2008年 | 1026篇 |
2007年 | 999篇 |
2006年 | 1018篇 |
2005年 | 912篇 |
2004年 | 508篇 |
2003年 | 386篇 |
2002年 | 298篇 |
2001年 | 337篇 |
2000年 | 408篇 |
1999年 | 569篇 |
1998年 | 519篇 |
1997年 | 455篇 |
1996年 | 364篇 |
1995年 | 362篇 |
1994年 | 298篇 |
1993年 | 316篇 |
1992年 | 258篇 |
1991年 | 238篇 |
1990年 | 179篇 |
1989年 | 142篇 |
1988年 | 130篇 |
1987年 | 88篇 |
1986年 | 48篇 |
1985年 | 24篇 |
1984年 | 24篇 |
1983年 | 17篇 |
1982年 | 14篇 |
1981年 | 17篇 |
1980年 | 11篇 |
1979年 | 5篇 |
1974年 | 6篇 |
1968年 | 6篇 |
1964年 | 3篇 |
1963年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Chih-Hua Chao Kuan-Hua Lin Chiung-Yao Huang Tsong-Long Hwang Chang-Feng Dai Hui-Chi Huang Jyh-Horng Sheu 《Marine drugs》2022,20(5)
A persistent study on soft coral Sarcophyton tortuosum resulted in the characterization of two new cembranolides, tortuolides A and B (1 and 2), and a new related diterpene, epi-sarcophytonolide Q. Their structures were determined not only by extensive spectroscopic analysis but also by DFT calculations of ECD and NMR data, the latter of which was combined with statistical analysis methods, e.g., DP4+ and J-DP4 approaches. Anti-inflammatory and cytotoxicity activities were evaluated in this study. 相似文献
2.
果实钙含量与低温伤害有着密切的关系,主要机制在于钙能防止果实的细胞膜损伤和渗漏,稳定膜结构和维持膜的完整性。胞外Ca^2+功能通过保护质膜的稳定性,使质膜具有较好的离子选择通透性,还可能对一些胞外酶或膜蛋白起调节作用。近年的研究表明,热激(非致死温度的热锻炼)处理能提高多种植物抗低温逆境的能力,还能引起胞内Ca^2+浓度迅速(1分钟之内)升高,因此可以认为,Ca^2+可能是启动热激反应的胞内关键因子。不知火杂柑品质优良,已有多篇文章对其进行研究。 相似文献
3.
本文通过对闽台农业合作发展现状及其作用的分析,并根据新形势发展的需要,提出了深化闽台农业合作领域的新思路。 相似文献
4.
5.
35种蜂花粉的活性物质分析 总被引:5,自引:0,他引:5
活性物质一般是指酶、维生素以及激素等,近年将磷脂也纳入活性物质。本文分析了35种蜂花粉中的葡萄糖氧化酶、磷脂以及生长激素等,这些物质对人体均有重要的生理作用。研究结果,除证明花粉中含有葡萄糖氧化酶及磷脂外,还发现了花粉含有人体生长激素 相似文献
6.
Xin-Yan Han Qi-Chun Huang Wei-Fen Li Jun-Fang Jiang Zi-Rong Xu 《Livestock Science》2008,119(1-3):216-220
The objective of this study was to investigate toxic effects of aflatoxin B1(AFB1) on growth performance, organs, hepatic enzyme activities, apparent digestibility of nutrients and digestive enzyme activities in ducks. Ninety 1-day-old Cherry Valley commercial ducks were designed to three treatment groups with three replicates of ten birds each. Group I (control) was fed conventional feed free of AFB1, group II or III was fed the diets containing 20 μg/kg or 40 μg/kg AFB1-contaminated rice respectively. The feeding trial lasted 6 weeks. The results were that decreased body weight gain and feed intake, increased feed to gain ratio and selected organ weights (liver, kidney and pancreas) were observed in AFB1-treated groups. The activities of serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were significantly increased in AFB1-contamined groups. The apparent digestibility of crude protein (CP) was significantly lower while activities of digestive enzyme from duodenum contents including protease, chymotrypsin, trypsin and amylase were increased in AFB1-treated group. These results indicated that AFB1 of feed could decrease growth performance and apparent digestibility of nutrients, change digestive enzyme activities of duodenum contents in duck. 相似文献
7.
8.
Dong-Hui Zhou Fu-Rong Zhao Hui-Yan Xia Min-Jun Xu Si-Yang Huang Hui-Qun Song Xing-Quan Zhu 《Irish veterinary journal》2013,66(1):1-4
Chlamydia spp. are obligate intracellular gram-negative bacteria that cause a wide range of significant diseases in humans and animals worldwide, resulting in significant economic losses. Chlamydial infection in cattle has been reported in many countries including China. However, there has been no survey of chlamydial infection of dairy cattle in Guangzhou, southern China. The objective of the present investigation was to examine the chlamydial seroprevalence in dairy cattle in Guangzhou, subtropical southern China by using an indirect hemagglutination assay (IHA). The overall seroprevalence of chlamydial infection in dairy cattle was 7.25% (29/400). Greater than or equal to eight-yr-old dairy cattle had the highest seroprevalence (10.34%), followed by those that were ≥ 6 years old or < 7 years old dairy cattle (10.20%), although there were no statistically significant differences among different groups (P > 0.05). Dairy cattle with 5 pregnancies had the highest seroprevalence (10.81%). These results indicate that chlamydial infection was present in dairy cattle in Guangzhou, subtropical southern China, and integrated strategies and measures should be executed to control and prevent chlamydial infection and disease outbreak in the study region. 相似文献
9.
湖南省根据地理区域和养殖业结构情况,合理布局建立了18个省级动物疫情测报站,通过对测报站辖区内及定点养殖场户的生产、免疫、疫病等情况进行持续跟踪调查和监测采样,评估动物群体免疫状态及疫情发生风险。管理上通过优化网络布局,提高诊断监测能力,通过强化培训和责任管理,提升动物疫情测报水平,确保了动物疫情测报质量。动物疫情测报站在发现新发重大动物疫病,评价强制免疫病种免疫效果,提供疫情预警预报基础数据以及指导养殖业生产等方面发挥了重要作用。今后需持续增加投入和监测科技含量,改善设施设备,稳定技术队伍,这是提高动物疫情测报监测的根本保障。 相似文献
10.
桑尺蠖和丝棉木金星尺蠖的微孢子虫对家蚕病原性和胚种传染性研究 总被引:2,自引:1,他引:2
从桑尺蠖(HemerophilaatrilineataButler)中分离的微孢子虫(简称桑尺蠖微孢子虫),形态为长卵圆形,大小为3.5~4.1×1.6~1.9μm。从丝棉木金星尺蠖(CalospilossuspectaWarren)中分离的微孢子虫(简称丝棉木金星尺蠖微孢子虫),形状为卵圆形,大小为3.2~3.7×1.6~2.1μm。两种微孢子虫均能感染寄生家蚕的主要组织器官,引起蚕儿发病,但致病力要比家蚕微孢子虫(Nosemabombycis)弱,且能经卵传染给下一代,其胚种传染率要比家蚕微孢子虫低。 相似文献